PHP 4, PHP 5, PHP 7, PHP 8
mt_srand - Seeds the Mersenne Twister Random Number Generator

mt_srand( [int$seed = 0], [int$mode = MT_RAND_MT19937] ): void

Seeds the random number generator with seed or with a random value if no seed is given.


There is no need to seed the random number generator with srand or mt_srand as this is done automatically.



An arbitrary int seed value.


Use one of the following constants to specify the implementation of the algorithm to use.

Constant Description
MT_RAND_MT19937 Uses the fixed, correct, Mersenne Twister implementation, available as of PHP 7.1.0.
MT_RAND_PHP Uses an incorrect Mersenne Twister implementation which was used as the default up till PHP 7.1.0. This mode is available for backward compatibility.

Return Values

No value is returned.


Version Description
7.1.0 srand has been made an alias of mt_srand.
7.1.0 mt_rand has been updated to use the fixed, correct, version of the Mersenne Twister algorithm. To fall back to the old behaviour, use mt_srand with MT_RAND_PHP as the second parameter.

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